The butterfly valves in existance today are usually built on the principle of soft gaskets. A very frequent valve type is illustrated in e.g. the Swedish patent specification 199078. With this valve type the whole of the valve housing is lined with a soft material, e.g. rubber or other polymer. A frequent thing is also to manufacture just the valve seat itself from a soft material. Examples of this valve type are illustrated in the Swedish patent specifications 175149 and 178131. There are also cases of the soft sealing element being instead placed on the sealing face of the throttle. Examples of this principle are shown in the Swedish patent specification 195072 and the German patent specifications 1011683 and 1232422. A disadvantage of soft sealing elements in butterfly valves is that their resistance to high-temperature media is often low. It is true that the insensitivness of synthetic rubber and certain other polymers to high temperatures has gradually improved, but still these kinds of material cannot in any way compare favourably with the resistance to high temperatures of steels and other metals and alloys. The same thing also applies to the resistance to certain chemically aggressive media. In these cases, too, the properties of high-alloyed stainless steels and other alloys are quite superior to those of soft materials of rubber type. These circumstances are, of course, well-known, and many a trial has been made with replacing the soft sealing elements by metallic ones. An example of this type of valve is disclosed in U.S. Pat. No. 4,058,290. A drawback of this valve, however is the wear between the throttle and the seat which has the form of a reselient ring, and also between the seat ring and the housing of the seat ring as the seat ring is displaced relative to the housing each time the throttle is opened or shut.